In addition to the government standard SEER or EER ratings found on the yellow sticker when you purchase an air conditioner, several other factors will contribute to your air conditioner's efficiency:
Sizing your air conditioner properly: An oversized unit will cycle on and off more frequently, causing it to work too hard, and potentially contributing to mold and mildew because it turns off before it has removed the moisture from the air. An undersized unit will work harder to distribute airflow and cause more wear on system components.
Ensuring that all ducts are free of leakage, blockage or other airflow problems: This should be done prior to installation and annually prior to the first use of the season.
Correct refrigerant level: According to Energy Star, an incorrect refrigerant level can reduce your central air conditioner's efficiency by 5 to 20%, and some studies have shown that as high as 75% of all installed cooling equipment has an incorrect level.
Reducing or rescheduling the use of other high-energy, heat-generating appliances like dryers and dishwashers: These are two of the highest energy-consuming appliances in the home. Air-dry dishes and clothes or use these appliances during cooler periods of the day.
Reducing the amount of heat that can enter your home by blocking or reflecting it away from windows, doors, the roof and attic: Providing shade around windows with trees or awnings, and closing drapes and blinds against the sunlight, can reduce the amount of heat actually entering a room.
Energy saving tips, from installation through to the ongoing operation and maintenance of your central air conditioner or window unit, can be found throughout this site.